Fearing that climate change could wipe out their entire Pacific archipelago, the leaders of Kiribati are considering an unusual backup plan: moving the populace to Fiji. The photo shows Kiribati's Tarawa atoll.

Richard Vogel/AP/File

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Girding communities now to bounce back from droughts, floods, heat waves, and severe storms they currently experience will go a long way to helping them adapt to long-term global warming.

The report surveys the current state of scientific knowledge about the impact global warming could have on nine types of extreme-weather events. The report spends the majority of its nine chapters exploring ways – from simple networks to spread warnings of a looming tropical cyclone to broader social changes, such as educating women and including them in community planning – to reduce the risk to people and property from weather extremes.

The volume is the strongest signal yet of a sea change in thinking during the past decade on adaptation to climate change.

Although the IPCC has dealt with the subject all along, adaptation is seen by many activist groups on global warming as a cop-out – a topic aimed at diverting attention from the need to reduce emissions of greenhouse gases.

But researchers have indicated that even if countries slammed the brakes on emissions today, the climate would continue to warm because carbon dioxide remains in the atmosphere for centuries. The gradual-but-relentless build-up of CO2 in the atmosphere since the dawn of the Industrial Revolution is an indication that humans are pumping it into the air faster than natural processes can remove the excess.

Increasingly, some degree of adaptation has come to be seen as a necessity, not a diversion.

Teasing out trends in extreme weather and identifying global warming's fingerprint are challenging, acknowledges Thomas Stocker, an atmospheric scientist at the University of Bern in Switzerland and co-chair of the IPCC working group that reviews the state of climate science. By definition, extreme weather events are relatively rare and require observations – of consistent, high quality – over long periods of time and with “extremely good spatial coverage,” he says.

But enough data have been accumulating during the past 60 years at least to begin the process. The report examines observed trends for the nine weather and climate features it considered, the likelihood that global warming is evident in the trends, and projections of how those trends may play out through the end of the century.

Some of the highest confidence levels across these three categories are for trends in extreme temperatures, with somewhat lower confidence levels for extreme precipitation.

While uncertainties remain, many of the approaches communities and countries can take to adapt to weather extremes fall into what Chris Field, co-chair of a second IPCC working group that focuses on impacts of climate change, dubs “low regrets measures.” These measures will provide significant benefits regardless of the factors underlying extreme-weather events.

Indeed, the cost from extreme-weather events has been rising.

Between 1970 and 1989, losses from disasters of all sorts averaged about $5 billion a year globally, notes Mark Way, who heads sustainable-development efforts in the Americas for the reinsurance firm Swiss Re. Since 1989, losses have averaged some $30 billion a year, driven in large part by weather-related disasters. Last year, losses in the US hit $35 billion, more than half the $61 billion in losses from severe weather globally.

At this point, the increase in losses has more to do with rapid population growth and a build-up of wealth in some of the most vulnerable areas – along coastlines, for instance – than with global warming, both the IPCC report and Mr. Way note.

One example of the impact adaptation can have shows up along the Indian Ocean coast.

The IPCC report cites key differences between the two countries. Bangladesh had more experience with direct hits and since the 1970s has worked with international aid groups to improve its ability to withstand the storms. It established warning systems. It built multistory shelters for people and raised artificial knolls to accommodate 300 to 400 head of livestock as a protection from storm surges. And the country has been trying to restore mangrove forests along the coast to help blunt storm surges.

Myanmar, by contrast, had little experience with storms and, importantly, some studies point to a closed, top-down regime as an impediment to building the kind of internal collaborative links between the national government and local communities that can help pave the way for projects to improve local resilience to severe weather.

Yet in some cases, more drastic action may be needed.

Earlier this month, the president of Kiribati told the Associated Press that his cabinet had approved the purchase of 6,000 acres on the main island of Fiji that would be the country's hedge against rising sea levels. Kiribati consists of 32 low-lying coral atolls and one island spanning more than 1.3 million square miles of the Pacific Ocean.

“As we look toward the future, the most difficult decisions in many settings are going to involve decisions about whether there should be large-scale migration or large-scale mobilization of communities, taking them out of the regions [that are] their cultural foundation and going to other places,” says Dr. Field, director of the Carnegie Institution of Washington's Department of Global Ecology, based at Stanford University in California.

One potential migration candidate: Mumbai. Much of the coastal city was swamped during floods in 2005. The megacity, with a population of more than 20 million, has what IPCC chairman Rajendra Pachauri calls a “terrible drainage system,” as well as vast slums where housing is particularly vulnerable to floods. To accommodate growth, builders drained wetlands and removed mangroves stands that ordinarily would have buffered the flooding.

For such locations, “climate change can impose additional stresses on top of the stresses already occurring,” Field adds. “For areas already close to the borderline, additional stresses might make them uninhabitable.”